How to Set Up And Tear Down A Database Between Tests In Fastapi?

In order to set up and tear down a database between tests in FastAPI, you can use testing fixtures. Testing fixtures are functions that are called before and after each test to set up and tear down the database connection.

To set up a database fixture, you can use the @pytest.fixture decorator in your test file. Inside the fixture function, you can create a new database connection and return it.

To tear down the database after the tests are run, you can use the yield keyword inside the fixture function. This will allow you to perform cleanup operations after each test is executed.

By using testing fixtures to set up and tear down the database between tests in FastAPI, you can ensure that each test has a clean database state and does not interfere with the results of other tests.

How to handle database rollback on test failure in FastAPI?

To handle database rollback on test failure in FastAPI, you can use pytest fixtures and the pytest-postgres plugin. Here's a step-by-step guide to achieve this:

1. Install pytest and pytest-postgres plugins:

1

pip install pytest pytest-postgres

1. Create a fixture for setting up and tearing down a test database:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31

import pytest
from fastapi.testclient import TestClient
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from app.database import Base

@pytest.fixture
def client():
    # Create a test database
    engine = create_engine("postgresql+psycopg2://postgres:password@localhost/test_db")
    Base.metadata.create_all(engine)
    
    # Create a session
    Session = sessionmaker(bind=engine)
    session = Session()

    # Start a transaction
    connection = engine.connect()
    transaction = connection.begin()

    # Create a FastAPI client
    app = create_app(session)
    with TestClient(app) as client:
        yield client

    # Rollback the transaction and disconnect
    transaction.rollback()
    connection.close()

    # Drop the test database
    Base.metadata.drop_all(engine)

1. Update your tests to use the client fixture:

1
2
3
4
5
6
7
8
9

def test_create_user(client):
    response = client.post("/users/", json={"name": "Alice"})
    assert response.status_code == 201
    assert response.json()["name"] == "Alice"

def test_get_users(client):
    response = client.get("/users/")
    assert response.status_code == 200
    assert len(response.json()) == 1

With this setup, the database transaction will be rolled back after each test, ensuring that the database is reset to its initial state. This helps in keeping your tests independent and predictable.

How to manage database versions for test runs in FastAPI?

Managing database versions for test runs in FastAPI can be done by using database migration tools such as Alembic or Flask-Migrate. These tools allow you to manage and track the changes made to the database schema over time.

Here are some steps to manage database versions for test runs in FastAPI:

1. Install a database migration tool like Alembic by adding it to your project's requirements.txt file:

1

alembic==1.7.1

1. Create an alembic.ini configuration file in the root directory of your project, and define the database connection URI and migration directory. Here is an example configuration:

1
2
3
4
5

# alembic.ini

[alembic]
script_location = alembic
sqlalchemy.url = DATABASE_URL

1. Initialize Alembic for your project by running the alembic init command in the terminal. This will create a new alembic directory with migration scripts.
2. Create a new migration script by running the alembic revision -m "create_table_name" command. This will create a new migration script with the specified name in the alembic/versions directory.
3. Define the database models in your FastAPI application using an ORM like SQLAlchemy. Make sure to import the models in the migration scripts to generate the database schema changes.
4. Apply the migration scripts to the database using the alembic upgrade head command. This will execute all pending migration scripts and update the database schema accordingly.
5. For testing purposes, you can create a separate database for running tests and apply the migration scripts to this database. This way, you can isolate the test data from the production database.

By following these steps, you can effectively manage database versions for test runs in FastAPI using a database migration tool like Alembic. This will help you keep track of changes to the database schema and ensure consistency across test environments.

How to create a schema for the database tables in FastAPI?

To create a schema for database tables in FastAPI, you can use Pydantic models. Pydantic is a data validation and parsing library in Python that works well with FastAPI.

Here is an example of how to create a schema for a database table using Pydantic in FastAPI:

1. Import the necessary modules:

1

from pydantic import BaseModel

1. Create a Pydantic model for your database table. For example, if you have a User table with id, name, and email columns, you can create a Pydantic model as follows:

1
2
3
4

class User(BaseModel):
    id: int
    name: str
    email: str

1. Use the Pydantic model in your FastAPI endpoints. You can use the Pydantic model as a request body or response model in your FastAPI endpoints to ensure type validation and serialization/deserialization of data.

1
2
3
4
5
6
7
8

from fastapi import FastAPI

app = FastAPI()

@app.post("/users/")
async def create_user(user: User):
    # Do something with the user data
    return {"message": "User created successfully"}

By using Pydantic models, you can easily define the structure of your database tables and ensure data consistency and type safety in your FastAPI application.